Transparent resin composition

Abstract

The present invention addresses the problem of providing a transparent resin composition capable of forming a cured product having excellent yellowing resistance and heat resistance, while suppressing warpage. The present invention relates to a transparent resin composition comprising (A) an epoxy resin having a fluoroalkyl group and / or an alicyclic structure and not having a siloxane structure, (B) an epoxy resin having a siloxane structure, and (C) a curing accelerator.

Description

Technical Field

[0001] The present invention relates to a transparent resin composition. Background Art

[0002] Transparent resin compositions are used as sealing materials, adhesives, and the like for transparent parts of electronic devices such as light-emitting diode (LED) devices and transparent flexible printed circuit boards (FPCs). For example, Patent Document 1 discloses a resin composition comprising a bisphenol AF epoxy resin, a thermoplastic resin, and a curing accelerator as an example of such a transparent resin composition.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-167428 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] Thermosetting resin compositions such as those described in Patent Document 1 may warp due to shrinkage during curing. Therefore, there is a need for resin compositions that can form cured products with excellent warping resistance. Furthermore, for use in transparent components of electronic devices such as LEDs and transparent FPCs, there is a need for transparent resin compositions that can form cured products with excellent yellowing resistance.

[0008] Methods for suppressing warping include using inorganic fillers or flexible resins. However, the former has the problem of significantly impairing the transparency of the cured product, while the latter has the problem of significantly lowering the glass transition temperature of the cured product and impairing heat resistance.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a transparent resin composition capable of forming a cured product having suppressed warping, excellent yellowing resistance, and excellent heat resistance.

[0010] The present invention that can achieve the above-mentioned object is as follows.

[0011] [1] A transparent resin composition comprising the following components (A) to (C):

[0012] (A) an epoxy resin having a fluoroalkyl group and / or an alicyclic structure and not having a siloxane structure,

[0013] (B) an epoxy resin having a siloxane structure, and

[0014] (C) Curing accelerator.

[0015] [2] The transparent resin composition according to [1], further comprising a polymer compound.

[0016] [3] The transparent resin composition according to [1] or [2], wherein the component (B) has a glycidyl group.

[0017] [4] The transparent resin composition according to any one of [1] to [3], wherein the content of the component (B) is 0.1 to 20% by mass relative to the non-volatile content of the transparent resin composition.

[0018] [5] The transparent resin composition according to any one of [1] to [4] above, wherein the number of epoxy groups in one molecule of component (B) is 2 to 10, and the epoxy equivalent of component (B) is 150 to 350 g / mol.

[0019] [6] A resin sheet having a laminated structure including a support and a transparent resin composition layer formed from the transparent resin composition according to any one of [1] to [5].

[0020] [7] An electronic device comprising a cured product layer formed from the transparent resin composition according to any one of [1] to [5].

[0021] Effects of the Invention

[0022] According to the present invention, a transparent resin composition capable of forming a cured product having suppressed warping, excellent yellowing resistance, and excellent heat resistance can be obtained. DETAILED DESCRIPTION

[0023] The present invention provides a transparent resin composition comprising the following components (A) to (C):

[0024] (A) an epoxy resin having a fluoroalkyl group and / or an alicyclic structure and not having a siloxane structure,

[0025] (B) an epoxy resin having a siloxane structure, and

[0026] (C) Curing accelerator.

[0027] Unless otherwise specified, in the present invention, each component may be used alone or in combination of two or more. Component (A) and the like will be described below in order.

[0028] <(A) Epoxy resin having a fluoroalkyl group and / or an alicyclic structure and not having a siloxane structure>

[0029] In the present invention, an epoxy resin having a fluoroalkyl group and / or an alicyclic structure and not having a siloxane structure is used as component (A). By using component (A), a cured product having excellent yellowing resistance can be formed.

[0030] In this specification, "epoxy resin" refers to a thermosetting compound containing epoxy groups and having an epoxy equivalent weight of 5,000 g / mol or less. The "epoxy equivalent weight" of an epoxy resin herein refers to the number of grams of epoxy resin per 1 mol of epoxy groups (unit: g / mol). The epoxy equivalent weight can be calculated according to the method specified in JIS K 7236. Theoretically, the epoxy equivalent weight can be calculated by dividing the molar mass (g / mol) of the epoxy resin by the number of epoxy groups in the resin.

[0031] The fluoroalkyl group that the component (A) may have is preferably C from the viewpoint of yellowing resistance. 1-6 Fluorinated alkyl, more preferably C 1-6 The perfluoroalkyl group is particularly preferably a trifluoromethyl group.

[0032] In this manual, “C x-y "(x and y: integers) means that the number of carbon atoms is x to y.

[0033] In the present specification, a "fluoroalkyl group" means an alkyl group substituted with a fluorine atom, and a "perfluoroalkyl group" means an alkyl group in which all hydrogen atoms are substituted with fluorine atoms.

[0034] In this manual, “C 1-6 The “fluoroalkyl group” includes, for example, fluoromethyl, difluoromethyl, perfluoromethyl (i.e., trifluoromethyl), 2-fluoroethyl, 2,2,2-trifluoroethyl, perfluoroethyl, 2,2-difluoropropyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, and perfluorohexyl.

[0035] In this manual, “C 1-6 Examples of "perfluoroalkyl" include the above-mentioned "C 1-6 Examples of "fluoroalkyl" include those which are perfluoroalkyl groups.

[0036] The alicyclic structure that the component (A) may have is preferably C from the viewpoint of yellowing resistance. 3-12 Alicyclic structure. The alicyclic structure may be any one of a monocyclic structure, a bicyclic structure, a condensed polycyclic structure, and a condensed polycyclic structure including a bicyclic ring. Component (A) may have one alicyclic structure or two or more alicyclic structures. The alicyclic structure that component (A) may have is more preferably C 3-8 Cycloalkane ring structure and / or dicyclopentadiene ring structure. That is, the (A) component is more preferably a fluoroalkyl group, C 3-8 An epoxy resin having at least one of a cycloalkane ring structure and a dicyclopentadiene ring structure and having no siloxane structure. In this specification, "C 3-8 The “cycloalkane ring” includes, for example, a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, and a cyclooctane ring.

[0037] The alicyclic structure that the component (A) may have is more preferably C 5-6 Cycloalkane ring structure (ie, cycloheptane ring structure, cyclohexane ring structure).

[0038] Examples of epoxy resins having a fluoroalkyl group and no siloxane structure include bisphenol AF epoxy resins having a trifluoromethyl group. Fluorinated epoxy resins described in WO2011 / 089947 can also be used as epoxy resins having a fluoroalkyl group and no siloxane structure. It should be noted that in this specification, "X-type epoxy resin" (example of X: bisphenol AF) refers to epoxy resins having a structure derived from X, as is well known in the art of epoxy resins.

[0039] Examples of epoxy resins having an alicyclic structure and no siloxane structure include bisphenol TMC epoxy resins having a cyclohexane ring structure and bisphenol Z epoxy resins having a cyclohexane ring structure. Furthermore, epoxy resins having a cyclohexane ring structure and no siloxane structure other than bisphenol TMC epoxy resins and bisphenol Z epoxy resins (e.g., "EHPE3150" manufactured by Daicel) can also be used as component (A).

[0040] From the viewpoint of yellowing resistance, component (A)

[0041] (i) preferably an epoxy resin having a fluoroalkyl group and not having a siloxane structure and / or an epoxy resin having an alicyclic structure and not having a siloxane structure,

[0042] (ii) more preferably selected from the group consisting of 1-6 Epoxy resins with fluoroalkyl groups and no siloxane structure, 3-8 at least one of an epoxy resin having a cycloalkane ring structure and not having a siloxane structure, and an epoxy resin having a dicyclopentadiene ring structure and not having a siloxane structure,

[0043] (iii) more preferably at least one selected from the group consisting of a bisphenol AF epoxy resin, an epoxy resin having a cyclohexane ring structure and no siloxane structure, and an epoxy resin having a dicyclopentadiene ring structure and no siloxane structure,

[0044] (iv) Particularly preferred are bisphenol AF type epoxy resins, epoxy resins having a cyclohexane ring structure and no siloxane structure, or epoxy resins having a dicyclopentadiene ring structure and no siloxane structure,

[0045] (v) Most preferably, it is a bisphenol AF type epoxy resin.

[0046] As the component (A), a commercially available product may be used, or a product produced by a known method (for example, the reaction of bisphenol AF, bisphenol TMC, or bisphenol Z with epichlorohydrin) may be used. Examples of commercially available products of the component (A) include “YX7760,” “YX8000,” and “YX8034” manufactured by Mitsubishi Chemical Corporation, “EHPE3150,” “EHPE3150CE,” “Celloxide 2021P,” “Celloxide 2081P,” “Celloxide 2000,” and “Celloxide 8000” manufactured by Daicel, “EP-4088S” manufactured by ADEKA, “HP-7200,” “HP-7200L,” and “HP-7200H” manufactured by DIC Corporation, “XD-1000” manufactured by Nippon Kayaku Co., Ltd., “Denacol EX-252” manufactured by Nagase ChemteX, “Shofree CDMDG” manufactured by Showa Denko K.K., “THI-DE,” “DE-102,” and “DE-103” manufactured by ENEOS, “DCPD-DE” manufactured by Nippon Materials Technology Co., Ltd., and “LDO” manufactured by SYMERISE.

[0047] The number of epoxy groups contained in the component (A) is preferably 2 to 10, more preferably 2 to 4, from the viewpoint of adhesion strength and warpage suppression of the cured product.

[0048] The epoxy equivalent of the component (A) is preferably 50 to 5,000 g / mol, more preferably 80 to 2,000 g / mol, and even more preferably 100 to 1,500 g / mol, from the viewpoint of the adhesion strength of the cured product.

[0049] From the perspective of yellowing resistance, the content of component (A) is preferably 20 to 89% by mass, more preferably 25 to 80% by mass, and even more preferably 30 to 75% by mass relative to the non-volatile content of the transparent resin composition. It should be noted that when multiple components (A) are used, the content thereof refers to the total content of the multiple components (A). The content of components other than component (A) refers to the total content of the components when multiple components are used.

[0050] <(B) Epoxy resin having a siloxane structure>

[0051] In the present invention, an epoxy resin having a siloxane structure is used as component (B). The use of component (B) can alleviate stress during heating of the transparent resin composition, resulting in a cured product with excellent warpage suppression. Component (B) also improves the yellowing resistance and heat resistance of the cured product.

[0052] In this specification, "siloxane structure" means a structure having a siloxane bond (Si-O-Si). The siloxane structure of component (B) may be linear, branched, or cyclic, preferably linear or cyclic, and more preferably linear.

[0053] Examples of the linear siloxane structure that the component (B) may have include linear polydi(C 1-6 Alkyl) siloxane structure. The C in the above siloxane structure 1-6 The alkyl group (eg, methyl group) may have a substituent.

[0054] In this manual, “C 1-6 The “alkyl group” includes, for example, methyl, dimethyl, ethyl, propyl, butyl, pentyl and hexyl.

[0055] The linear siloxane structure is preferably a polydimethylsiloxane structure. The methyl group in the polydimethylsiloxane structure may have a substituent.

[0056] Examples of the cyclic siloxane structure that the component (B) may have include hexa(C 1-6 Alkyl) cyclotrisiloxane structure, octa(C 1-6 Alkyl) cyclotetrasiloxane structure, deca(C 1-6 alkyl)cyclopentasiloxane structure, preferably octa(C 1-6 Alkyl) cyclotetrasiloxane structure. The C in the aforementioned cyclic siloxane structure 1-6 The alkyl group (eg, methyl group) may have a substituent.

[0057] Component (B) preferably has a glycidyl group. Component (B) having a glycidyl group has better compatibility with component (A) than component (B) having an alicyclic epoxy group. By using component (B) having a glycidyl group, a cured product with low haze and high transparency can be formed. It should be noted that, in this specification, "alicyclic epoxy group" refers to a condensed ring group comprising an alicyclic group and an oxirane ring, obtained by forming an oxirane ring (epoxy group) from two adjacent carbon atoms and an oxygen atom constituting the alicyclic group.

[0058] (B) component is preferably a linear polydimethylsiloxane having an epoxy group and / or an octa(C) 1-6 alkyl) cyclotetrasiloxane, more preferably a linear polydimethylsiloxane having a glycidyl group and / or an octa(C 1-6 It is preferably a linear polydimethylsiloxane having a glycidyl group.

[0059] The number of Si atoms in the siloxane structure of the component (B) is preferably 2 to 12, more preferably 2 to 8, from the viewpoint of compatibility with the component (A).

[0060] The number of epoxy groups in one molecule of the component (B) is preferably 2 to 10, more preferably 2 to 4, from the viewpoint of adhesion strength and warpage suppression of the cured product.

[0061] The epoxy equivalent of the component (B) is preferably 100 to 350 g / mol, more preferably 120 to 330 g / mol, and even more preferably 150 to 300 g / mol, from the viewpoint of the adhesion strength of the cured product.

[0062] As the component (B), a commercially available product can be used. Examples of commercially available products of the component (B) include "X-22-163," "X-22-163A," "X-22-163B," "X-22-163C," "X-22-169B," "X-22-169AS," "X-22-343," "X-22-2046," "X-22-2000," "X-40-2670," "X-40-2678," "X-40-2728," "KR-470," "KF-105," "KF-101," "KF-102," and "KF-1001" manufactured by Shin-Etsu Chemical Co., Ltd.

[0063] From the viewpoint of warpage suppression and heat resistance, the content of the component (B) is preferably 0.1 to 20 mass %, more preferably 0.5 to 18 mass %, and even more preferably 1 to 15 mass % relative to the nonvolatile content of the transparent resin composition.

[0064] <(C) Curing accelerator>

[0065] In the present invention, a curing accelerator is used as component (C). In this specification, the term "curing accelerator" refers to an additive that accelerates the curing reaction between epoxy resins. In the field of epoxy resins, additives that accelerate the curing reaction between epoxy resins are sometimes referred to as curing agents (particularly catalyst-type curing agents).

[0066] Examples of the curing accelerator as the component (C) include phosphorus-based curing accelerators (eg, phosphonium salts, phosphines), imidazole-based curing accelerators, amine-based curing accelerators, guanidine-based curing accelerators, and metal-based curing accelerators.

[0067] Examples of the phosphonium salt include phosphonium borate compounds, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, n-butylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate. Commercially available phosphonium salts can be used. Examples of such commercially available products include "TBP-DA" manufactured by Hokko Chemical Industry Co., Ltd.

[0068] Examples of the phosphine include triphenylphosphine, tricyclohexylphosphine, tributylphosphine, and methyldiphenylphosphine.

[0069] Examples of the imidazole curing accelerator include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1') Imidazole compounds such as 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, and adducts of imidazole compounds with epoxy resins. Commercially available imidazole curing accelerators can be used. Examples of such commercially available products include "P200-H50" manufactured by Mitsubishi Chemical Corporation and "1B2PZ-10M" manufactured by Shikoku Chemicals.

[0070] Examples of the amine-based curing accelerator include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene.

[0071] Examples of the guanidine-based curing accelerator include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanidine, 1-ethylbiguanidine, 1-n-butylbiguanidine, 1-n-octadecylbiguanidine, 1,1-dimethylbiguanidine, 1,1-diethylbiguanidine, 1-cyclohexylbiguanidine, 1-allylbiguanidine, 1-phenylbiguanidine, and 1-(o-tolyl)biguanidine.

[0072] Examples of metallic curing accelerators include organometallic complexes or organometallic salts in which the metal is cobalt, copper, zinc, iron, nickel, manganese, or tin. Examples of organometallic complexes include organocobalt complexes such as cobalt (II) acetylacetonate and cobalt (III) acetylacetonate, organocopper complexes such as copper (II) acetylacetonate, organozinc complexes such as zinc (II) acetylacetonate, organoferric complexes such as iron (III) acetylacetonate, organonickel complexes such as nickel (II) acetylacetonate, and organomanganese complexes such as manganese (II) acetylacetonate. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

[0073] From the viewpoint of storage stability of the transparent resin composition, the content of the component (C) is preferably 0.1 to 5 mass %, more preferably 0.3 to 4 mass %, and even more preferably 0.5 to 3 mass % relative to the nonvolatile content of the transparent resin composition.

[0074] From the viewpoint of yellowing resistance, it is preferred to use a phosphonium salt as a curing accelerator. Relative to the entire component (C), the content of the phosphonium salt in the transparent resin composition of the present invention is preferably 90 to 100% by mass, more preferably 95 to 100% by mass. From the viewpoint of yellowing resistance, it is most preferred that component (C) is a phosphonium salt, that is, component (C) as a whole is composed of a phosphonium salt.

[0075] <Other ingredients>

[0076] The transparent resin composition of the present invention may further contain components other than components (A) to (C) (sometimes referred to as "other components" in this specification) within the range that does not hinder the effects of the present invention. Examples of other components include polymer compounds, epoxy resins other than components (A) and (B), organic solvents, light stabilizers, silane coupling agents, antioxidants, and ultraviolet absorbers. Each of the other components may be used alone or in combination of two or more. The other components are described below in order.

[0077] (Polymer compound)

[0078] In order to form a film of the transparent resin composition, it is preferable to use a polymer compound. In this specification, the "polymer compound" means a compound having a weight average molecular weight (hereinafter sometimes referred to as "Mw") of 1,000 or more. The Mw can be measured by gel permeation chromatography (GPC).

[0079] Examples of polymer compounds include phenoxy resins, polyester polyols, polyether polyols, polycarbonate polyols, and (meth)acrylic resins. Preferred Mw values ​​for phenoxy resins are described below. Polyester polyols preferably have an Mw value of 1,000 to 10,000. Polyether polyols preferably have an Mw value of 1,000 to 10,000. Polycarbonate polyols preferably have an Mw value of 1,000 to 10,000. (Meth)acrylic resins preferably have an Mw value of 1,000 to 500,000.

[0080] The polymer compound is preferably a phenoxy resin. In this specification, "phenoxy resin" means a high molecular weight polyhydroxy polyether having a structure derived from bisphenols. Examples of phenoxy resins include those obtained by the reaction of bisphenols with epichlorohydrin and those obtained by the reaction of bisphenol-type epoxy resins. Here, "bisphenol-type epoxy resin" means an epoxy resin having a structure derived from bisphenols (e.g., bisphenol AF). It should be noted that the phenoxy resin may have a structure other than that derived from bisphenols.

[0081] Phenoxy resins may or may not have epoxy groups. In the present invention, "phenoxy resins having epoxy groups" are distinguished from "epoxy resins" by their epoxy equivalent. That is, in the present invention, those having an epoxy equivalent of more than 5000 g / mol are classified as "phenoxy resins having epoxy groups", and those having an epoxy equivalent of 5000 g / mol or less are classified as "epoxy resins". From the viewpoint of film formation of the transparent resin composition and the adhesion strength of the cured product, the epoxy equivalent of the phenoxy resin having epoxy groups is preferably greater than 5,000 g / mol and less than 40,000 g / mol, more preferably 7,000 to 35,000 g / mol, and even more preferably 8,000 to 30,000 g / mol.

[0082] The weight average molecular weight of the phenoxy resin is preferably greater than 10,000 and 100,000 or less, more preferably 20,000 to 80,000, and even more preferably 25,000 to 60,000, from the viewpoint of compatibility in the transparent resin composition and adhesion strength of the cured product.

[0083] Phenoxy resins may be commercially available products or those produced by known methods (e.g., reaction of bisphenols with epichlorohydrin). Examples of commercially available products include "YX7200B35," "1256," "4250," "YX8100," "YX6954BH30," "YX7553BH30," "YL7769BH30," "YX7876B40," "YL9008B40," "YL6794," "YL7213," "YL7891BH30," and "YL7482" manufactured by Mitsubishi Chemical Corporation, and "YP-50," "YP-70S," "FX-293," and "FX280S" manufactured by Nippon Steel Chemicals & Materials Co., Ltd.

[0084] From the perspective of yellowing resistance, phenoxy resin

[0085] (i) preferably a phenoxy resin having a fluoroalkyl group and / or a phenoxy resin having an alicyclic structure,

[0086] (ii) more preferably having C 1-6 Fluoroalkyl phenoxy resin and / or C 3-8 Phenoxy resin with cycloalkane ring structure,

[0087] (iii) It is further preferred that the 1-6 Phenoxy resins containing perfluoroalkyl and / or C 5-6 Phenoxy resin with cycloalkane ring structure,

[0088] (iv) further preferably a phenoxy resin having a trifluoromethyl group and / or a phenoxy resin having a cyclohexane ring structure,

[0089] (v) Bisphenol AF type phenoxy resin and / or phenoxy resin having a cyclohexane ring structure are particularly preferred.

[0090] (vi) Most preferably, it is a phenoxy resin having a cyclohexane ring structure.

[0091] When a polymer compound is used, its content is preferably 5 to 50% by mass, more preferably 7.5 to 45% by mass, and even more preferably 10 to 40% by mass relative to the nonvolatile components of the transparent resin composition, from the viewpoint of film formation of the transparent resin composition and adhesion strength of the cured product.

[0092] When a phenoxy resin is used as the polymer compound, from the viewpoint of film formation of the transparent resin composition and the adhesion strength of the cured product, the content of the phenoxy resin is preferably 5 to 50% by mass, more preferably 7.5 to 45% by mass, and even more preferably 10 to 40% by mass relative to the non-volatile components of the transparent resin composition.

[0093] (Epoxy resin other than component (A) and component (B))

[0094] The transparent resin composition of the present invention may further contain an epoxy resin other than components (A) and (B) (sometimes referred to simply as "other epoxy resins" in this specification) within a range that does not impair the effects of the present invention (i.e., warpage suppression, yellowing resistance, and heat resistance).

[0095] There are no particular limitations on other epoxy resins, and known epoxy resins can be used. Examples of other epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, biphenyl epoxy resins, biphenyl alkyl epoxy resins, naphthol epoxy resins, and naphthalene epoxy resins. Other epoxy resins may also include mixtures of multiple epoxy resins (e.g., mixtures of bisphenol A epoxy resins and bisphenol F epoxy resins).

[0096] From the viewpoint of the adhesion strength of the cured product of the transparent resin composition, the epoxy equivalent of the other epoxy resin is preferably 50 to 5,000 g / mol, more preferably 80 to 2,000 g / mol, and even more preferably 100 to 1,500 g / mol.

[0097] When other epoxy resins are used to improve the toughness of the cured product, their content is preferably 1 to 40% by mass, more preferably 5 to 35% by mass, and even more preferably 10 to 30% by mass relative to the nonvolatile components of the transparent resin composition so as not to inhibit the effects of the present invention.

[0098] In order not to impair the effects of the present invention, the transparent resin composition of the present invention preferably contains no other epoxy resin, or contains other epoxy resins in an amount of 50% by mass or less relative to the total of component (A), component (B), and other epoxy resins (i.e., the amount of other epoxy resins is limited to 50% by mass or less relative to the total of component (A), component (B), and other epoxy resins). The amount of other epoxy resins is more preferably 40% by mass or less, and even more preferably 35% by mass or less relative to the total of component (A), component (B), and other epoxy resins.

[0099] (Organic Solvent)

[0100] The transparent resin composition of the present invention may contain an organic solvent. That is, the transparent resin composition of the present invention may be a varnish-like transparent resin composition containing an organic solvent.

[0101] Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone (MEK), and cyclohexanone; acetates such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, and carbitol acetate; cellosolves such as cellosolve; carbitols such as butyl carbitol; aromatic hydrocarbons such as toluene and xylene; dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

[0102] When an organic solvent is used, the content thereof is preferably 5 to 50% by mass, more preferably 10 to 45% by mass, and even more preferably 15 to 40% by mass, based on the entire transparent resin composition.

[0103] In order to improve the yellowing resistance of the cured product, the transparent resin composition of the present invention may contain a light stabilizer. As the light stabilizer, for example, a hindered amine light stabilizer can be mentioned. As the hindered amine light stabilizer, for example, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-butyl-2-(4-hydroxy-3,5-di-tert-butylbenzyl) malonate, butane-1,2,3,4-tetracarboxylic acid tetra(1,2,2,6,6-pentamethyl-4-piperidyl) ester, 1,2,3 ,4-butanetetracarboxylic acid tetrakis(2,2,6,6-tetramethyl-4-piperidinyl ester), mixed ester of 1,2,3,4-butanetetracarboxylic acid with 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, bis(1,2,2,6,6-pentamethyl-4-piperidinyl sebacate).

[0104] Commercially available light stabilizers can be used. Examples of such commercially available products include "Tinuvin 770DF" and "Tinuvin PA 144" manufactured by BASF, and "Adekastab LA-52," "Adekastab LA-57," "Adekastab LA-63P," "Adekastab LA-68," "Adekastab LA-72," "Adekastab LA-81," and "Adekastab LA-87" manufactured by ADEKA.

[0105] When a light stabilizer is used, its content is preferably 0.1 to 10% by mass, more preferably 0.4 to 8% by mass, and even more preferably 0.8 to 5% by mass relative to the nonvolatile components of the transparent resin composition from the viewpoint of improving yellowing resistance.

[0106] (Silane coupling agent)

[0107] The transparent resin composition of the present invention may contain a silane coupling agent in order to improve the adhesion strength of a cured product obtained from the composition to glass.

[0108] From the perspective of storage stability of the transparent resin composition, the silane coupling agent is preferably at least one selected from a (meth)acryloyl group-containing silane coupling agent, an epoxy group-containing silane coupling agent, and a vinyl group-containing silane coupling agent. To suppress warping caused by shrinkage during curing of the transparent resin composition, the silane coupling agent is more preferably a (meth)acryloyl group-containing silane coupling agent, and even more preferably an acryl group-containing silane coupling agent.

[0109] Examples of the (meth)acryloyl group-containing silane coupling agent include 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 8-methacryloxyoctyltrimethoxysilane.

[0110] Examples of the epoxy group-containing silane coupling agent include 2-(3,4-ethoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 8-glycidoxyoctyltrimethoxysilane.

[0111] Examples of the vinyl group-containing silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, and 7-octenyltrimethoxysilane.

[0112] A commercially available silane coupling agent can be used. Examples of such commercially available products include "KBM-5103," "KBM-502," "KBM-503," "KBE-502," "KBE-503," "KBM-5803," "KBM-303," "KBM-402," "KBM-403," "KBE-402," "KBE-403," "KBM-4803," "KBM-1003," "KBE-1003," and "KBM-1083" manufactured by Shin-Etsu Chemical Co., Ltd.

[0113] From the perspective of adhesion strength of the cured product, the silane coupling agent is preferably at least one selected from 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 8-methacryloxyoctyltrimethoxysilane, 2-(3,4-ethoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 8-glycidoxyoctyltrimethoxysilane, vinyltrimethoxysilane, and 7-octenyltrimethoxysilane. 3-acryloxypropyltrimethoxysilane and / or 3-glycidoxypropyltrimethoxysilane are more preferred. From the perspective of suppressing warpage of the cured product, the silane coupling agent is more preferably 3-acryloxypropyltrimethoxysilane.

[0114] When a silane coupling agent is used, its content is preferably 0.1 to 20% by mass, more preferably 0.4 to 15% by mass, and even more preferably 0.8 to 10% by mass relative to the nonvolatile content of the transparent resin composition, from the viewpoint of adhesion strength of the cured product.

[0115] (Antioxidant)

[0116] Examples of the antioxidant include hindered phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. Specific examples of the antioxidant include butylated hydroxytoluene (BHT), pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) ("IRGANOX 1010" manufactured by BASF Japan), 2,2-thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ("IRGANOX 1035" manufactured by BASF Japan), and 1,3,5-tris[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione ("IRGANOX 3114" manufactured by BASF Japan).

[0117] (UV absorber)

[0118] Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, and triazine-based ultraviolet absorbers.

[0119] Examples of the benzophenone-based ultraviolet absorber include 2-hydroxy-4-octyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy-4-n-octylbenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 2,2'-dihydroxy-4-methoxybenzophenone, and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone.

[0120] Examples of the benzotriazole-based ultraviolet absorber include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-[2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl]benzotriazole, 2-(2'-hydroxy-3',5-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, and 2,2-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2N-benzotriazol-2-yl)phenol].

[0121] Examples of the salicylic acid-based ultraviolet absorber include phenyl salicylate, 4-tert-butylphenyl-2-hydroxybenzoate, phenyl-2-hydroxybenzoate, 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate, and hexadecyl-3,5-di-tert-butyl-4-hydroxybenzoate.

[0122] Examples of the triazine-based ultraviolet absorber include 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxyphenol, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol, 2-[4,6-bis(dimethylphenyl)-1,3,5-triazin-2-yl]-5-"3-[(2-ethylhexyl)oxy]-2-hydroxypropoxy"-phenol, and 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine.

[0123] As another ultraviolet absorber, ethyl 2-cyano-3,3-diphenylacrylate is mentioned, for example.

[0124] Commercially available UV absorbers can be used. Examples of such commercially available products include "Chimassorb 81FL," "Tinuvin P," "Tinuvin 213," "Tinuvin 234," "Tinuvin 326," "Tinuvin 360," "Tinuvin 571," "Tinuvin 1577ED," and "Tinuvin 120" manufactured by BASF, "EVERSORB 11," "EVERSORB 12," "EVERSORB 40," "EVERSORB 71," "EVERSORB 73," "EVERSORB 78," "EVERSORB 80," and "EVERSORB 109" manufactured by Sanyo Trading Co., Ltd., "5405" manufactured by Kusumoto Chemicals Co., Ltd., and "Adekastab LA-46" and "Adekastab LA-F70" manufactured by Adeka Corporation.

[0125] <Inorganic fillers>

[0126] The transparent resin composition of the present invention may further contain an inorganic filler within the range of maintaining the transparency of the cured product. From the viewpoint of transparency, the transparent resin composition of the present invention does not contain an inorganic filler, or contains an inorganic filler in an amount of 30% by mass or less relative to the non-volatile components of the transparent resin composition (i.e., the content of the inorganic filler is suppressed to 30% by mass or less relative to the non-volatile components of the transparent resin composition). The content of the inorganic filler is more preferably 20% by mass or less, further preferably 10% by mass or less, and particularly preferably 5% by mass or less relative to the non-volatile components of the transparent resin composition.

[0127] <Average value of total light transmittance at wavelengths of 380 to 780 nm of a transparent resin composition layer having a thickness of 60 μm>

[0128] The average total light transmittance of a 60 μm thick transparent resin composition layer formed from the transparent resin composition of the present invention at a wavelength of 380 to 780 nm is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. This average value can be measured by the method described in the Examples section below.

[0129] <Average value of total light transmittance at wavelengths of 380 to 780 nm for a cured layer with a thickness of 60 μm>

[0130] The average total light transmittance of a 60 μm thick cured layer formed from the transparent resin composition of the present invention at a wavelength of 380 to 780 nm is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. This average value can be measured by the method described in the Examples section below.

[0131] <Resin Sheet>

[0132] The present invention provides a resin sheet having a laminated structure comprising a support and a transparent resin composition layer formed from the transparent resin composition of the present invention. A protective film may be used in the present invention. That is, the resin sheet of the present invention may have a laminated structure comprising, in sequence, a support, a transparent resin composition layer, and a protective film. Other layers (e.g., a release layer, an adhesive layer) may also be present between the support and the transparent resin composition layer, and between the transparent resin composition layer and the protective film.

[0133] The thickness of the transparent resin composition layer is not particularly limited, but is preferably 1 μm or more, more preferably 1.5 μm or more, further preferably 2 μm or more, particularly preferably 5 μm or more, and preferably 150 μm or less, preferably 120 μm or less, more preferably 100 μm or less, further preferably 80 μm or less.

[0134] Examples of the support include plastic films such as polyethylene, polypropylene, polyvinyl chloride, cycloolefin polymers, polyethylene terephthalate (hereinafter sometimes referred to as "PET"), polyethylene naphthalate, polycarbonate, and polyimide, and metal foils such as aluminum foil, stainless steel foil, and copper foil. Among them, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred. The support may have a release layer on the surface that is bonded to the transparent resin composition layer. Examples of release agents for forming the release layer include silicone resin release agents, alkyd resin release agents, and fluororesin release agents. The surface of the support that is bonded to the transparent resin composition layer may be subjected to matting treatment, corona treatment, or antistatic treatment.

[0135] The thickness of the support is not particularly limited, but is preferably 10 to 250 μm, more preferably 20 to 200 μm. When a support with a release layer is used, the thickness of the entire support with a release layer is preferably within the above range.

[0136] A resin sheet can be produced, for example, by (1) preparing a varnish-like transparent resin composition, (2) applying the varnish-like transparent resin composition onto a support using a die coater or the like to form a coating film, and (3) drying the resulting coating film to form a transparent resin composition layer. The method for producing the varnish-like transparent resin composition is not particularly limited, and the varnish-like transparent resin composition can be produced by mixing an organic solvent with the various components using a known device such as a rotary mixer.

[0137] The coating film can be dried by known methods such as heating and blowing hot air. The drying conditions are not particularly limited. It is preferred to dry until the content of the organic solvent in the transparent resin composition layer is 10% by mass or less. The content of the organic solvent in the dried transparent resin composition layer is more preferably 5% by mass or less. The drying time and drying temperature vary depending on the content of the organic solvent in the varnish-like transparent resin composition and its boiling point. The drying temperature is, for example, about 50 to 150° C., and the drying time is, for example, about 3 to 10 minutes.

[0138] The resin sheet can be stored in a roll. If the resin sheet has a protective film, the resin sheet can be used by peeling off the protective film.

[0139] <Electronic devices>

[0140] The present invention also provides an electronic device comprising a cured product layer formed from the transparent resin composition of the present invention. Examples of the electronic device include LED devices and electronic devices comprising transparent FPCs.

[0141] The cured product layer is preferably formed by heating the transparent resin composition layer. As a heating method, there is no particular limitation, and the transparent resin composition layer can be heated by a known device (for example, a hot air circulation oven, an infrared heater, a hot air gun, a high-frequency induction heating device). From the viewpoint of promoting the curing reaction, the curing temperature is preferably 80°C or more, more preferably 100°C or more, and from the viewpoint of preventing the coloring of the cured product layer, it is preferably 210°C or less, more preferably 180°C or less. In addition, the curing time is preferably 10 minutes or more, more preferably 20 minutes or more, preferably 180 minutes or less, more preferably 120 minutes or less.

[0142] Example

[0143] The present invention is further described below with reference to Examples. However, the present invention is not limited to the following Examples and can be implemented with appropriate modifications within the scope of the above- and below-described gist. Such modifications are encompassed within the technical scope of the present invention. It should be noted that "parts" and "%" in component amounts refer to "parts by mass" and "mass %," respectively, unless otherwise specified.

[0144] The components used in Examples and Comparative Examples are as follows.

[0145] <(A)Component>

[0146] YX7760 (Mitsubishi Chemical Corporation, bisphenol AF epoxy resin, solid at room temperature, epoxy equivalent: 245 g / mol)

[0147] EHPE3150 (manufactured by Daicel, an epoxy resin with a cyclohexane ring structure, solid at room temperature, epoxy equivalent weight: 180 g / mol)

[0148] EP-4088S (manufactured by ADEKA, an epoxy resin with a dicyclopentadiene structure, liquid at room temperature, epoxy equivalent: 170 g / mol)

[0149] <(B) Ingredient>

[0150] "X-22-163" (manufactured by Shin-Etsu Chemical Co., Ltd., linear polydimethylsiloxane having glycidyl groups at both ends (i.e., two glycidyl groups in the molecule), number of Si atoms in the siloxane structure: 2, epoxy equivalent: 200 g / mol)

[0151] "X-40-2728" (manufactured by Shin-Etsu Chemical Co., Ltd., cyclic siloxane having two glycidyl groups in the molecule, number of Si atoms in the siloxane structure: 4, epoxy equivalent: 280 g / mol)

[0152] “KR-470” (manufactured by Shin-Etsu Chemical Co., Ltd., cyclic siloxane having four alicyclic epoxy groups in the molecule, number of Si atoms in the siloxane structure: 4, epoxy equivalent: 200 g / mol)

[0153] <Other epoxy resins>

[0154] "ZX-1059" (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., a mixture of bisphenol A epoxy resin (50%) and bisphenol F epoxy resin (50%), liquid at room temperature, epoxy equivalent: 165 g / mol)

[0155] <(C) Ingredient>

[0156] "TBP-DA" (manufactured by Hokuko Chemical Industry Co., Ltd., n-butylphosphonium decanoate)

[0157] <Phenoxy resin>

[0158] "YX7200B35" (Mitsubishi Chemical Corporation, solution of a phenoxy resin having a structure derived from biphenyl and bisphenol TMC, organic solvent: methyl ethyl ketone, non-volatile content: 35%, weight average molecular weight: 30,000, epoxy equivalent: 9,000 g / mol)

[0159] Light stabilizers

[0160] LA-52 (manufactured by ADEKA, tetrakis(2,2,6,6-tetramethyl-4-piperidinyl)-1,2,3,4-butanetetracarboxylate, CAS No. 91788-83-9)

[0161] <Silane coupling agent>

[0162] "KBM-403" (manufactured by Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltrimethoxysilane)

[0163] "KBM-5103" (manufactured by Shin-Etsu Chemical Co., Ltd., 3-acryloxypropyltrimethoxysilane)

[0164] <Preparation of Transparent Resin Composition>

[0165] <Example 1>

[0166] 24 parts of a phenoxy resin solution "YX7200B35" (phenoxy resin: 8.4 parts), 12 parts of component (A) "YX7760", 6 parts of another epoxy resin "ZX-1059", and 1 part of component (B) "X-22-163" were mixed. The resulting mixture was heated to dissolve components (A) and (B). 0.4 parts of component (C) "TBP-DA" was added to the mixture to prepare a varnish-like transparent resin composition.

[0167] <Example 2>

[0168] A varnish-like transparent resin composition was prepared in the same manner as in Example 1 except that 12 parts of "EHPE3150" were used in place of 12 parts of "YX7760" (Component (A).

[0169] <Example 3>

[0170] A varnish-like transparent resin composition was prepared in the same manner as in Example 1 except that 18 parts of the component (A) "EP-4088S" was used instead of 12 parts of the component (A) "YX7760" and 6 parts of the other epoxy resin "ZX-1059".

[0171] <Example 4>

[0172] (B) A varnish-like transparent resin composition was prepared in the same manner as in Example 1 except that the amount of component "X-22-163" used was changed from 1 part to 3 parts.

[0173] <Example 5>

[0174] A varnish-like transparent resin composition was prepared in the same manner as in Example 1 except that 1 part of the component (B) "X-40-2728" was used in place of 1 part of the component (B) "X-22-163".

[0175] <Example 6>

[0176] A varnish-like transparent resin composition was prepared in the same manner as in Example 1 except that 1 part of the component (B) "KR-470" was used in place of 1 part of the component (B) "X-22-163".

[0177] <Example 7>

[0178] A varnish-like transparent resin composition was prepared in the same manner as in Example 1 except that 0.26 parts of a light stabilizer "LA-52" was added.

[0179] <Example 8>

[0180] A varnish-like transparent resin composition was prepared in the same manner as in Example 1 except that 0.26 parts of a silane coupling agent "KBM-403" was added.

[0181] <Example 9>

[0182] A varnish-like transparent resin composition was prepared in the same manner as in Example 1 except that 0.26 parts of a silane coupling agent "KBM-5103" was added.

[0183] <Comparative Example 1>

[0184] A varnish-like transparent resin composition was prepared in the same manner as in Example 1 except that 18 parts of another epoxy resin "ZX-1059" was used instead of 12 parts of "YX7760" (Component (A)) and 6 parts of another epoxy resin "ZX-1059".

[0185] Comparative Example 2

[0186] A varnish-like transparent resin composition was prepared in the same manner as in Example 1 except that the (B) component "X-22-163" was not used.

[0187] Preparation of evaluation samples

[0188] The varnish-like transparent resin composition prepared in the examples or comparative examples was applied to a PET film ("LUMIRRORFILM 188 μm" manufactured by ASONE) using a die coater so that the thickness of the dried transparent resin composition layer was 60 μm. The film was dried at 100° C. for 7 minutes to form a transparent resin composition layer, thereby obtaining a resin sheet having a laminated structure of "PET film / transparent resin composition layer".

[0189] The obtained resin sheet was heated at 150°C for 90 minutes to thermally cure the transparent resin composition layer, thereby obtaining a sheet having a laminated structure of "PET film / cured material layer" (hereinafter referred to as "cured material sheet (1)").

[0190] <Measurement of total light transmittance>

[0191] The portion of the transparent resin composition layer of the resin sheet obtained in <Preparation of Evaluation Samples> with uniform thickness and the portion of the cured product layer of the cured product sheet with uniform thickness were cut into 3 cm squares, and the portions ... A fiber-type spectrophotometer with an integrating sphere ("MCPD-7700" manufactured by Otsuka Electronics Co., Ltd.) was used, with the distance between the integrating sphere and the sample set at 30 mm. These measurements were made using the PET film used in the production as a reference, and the average total light transmittance of the transparent resin composition layer and the cured product layer at wavelengths of 380 to 780 nm was calculated. The results are reported in Table 1 below. Since the average total light transmittance of the transparent resin composition layer and the cured product layer was the same, only one value is reported in Table 1 below.

[0192] <Haze measurement>

[0193] Haze (%) was measured in accordance with JIS K7136. Specifically, a portion of the cured layer of the cured product sheet (1) obtained in "Preparation of Evaluation Samples" having a uniform thickness was cut into 3 cm squares. The haze (%) was measured using a haze meter HZ-V3 (halogen lamp) manufactured by SUGA Testing Instruments Co., Ltd., with air as a reference, under a D65 light source. The results are reported in Table 1 below. The smaller the haze value, the more transparent the cured product.

[0194] <Measurement of b* and evaluation of yellowing resistance>

[0195] A portion of the cured product layer of the cured product sheet (1) obtained in the <Preparation of Evaluation Samples> having a uniform thickness was cut out and the cured product layer was cut out using a Using a fiber-type spectrophotometer with an integrating sphere (MCPD-7700, manufactured by Otsuka Electronics Co., Ltd.), with the integrating sphere and sample at a distance of 30 mm and air as the reference, colorimetry was performed under conditions of a viewing angle of 2 degrees and illuminant D65 to calculate b* in the L*a*b* colorimetric system. The cured sheet was then placed in an oven at 200°C for 1 hour, removed from the oven, and allowed to cool to room temperature, whereupon b* was measured in the same manner as above. The rate of change in b* before and after oven heating (Δb*) was calculated using the following formula:

[0196] Δb*=b* after oven heating / b* before oven heating

[0197] The yellowing resistance was evaluated according to the following criteria. The results are shown in Table 1 below.

[0198] (Evaluation criteria for yellowing resistance)

[0199] Good (○): Δb* less than 2.0

[0200] Acceptable (△): Δb* is 2.0 or more and less than 3.0

[0201] Defective (×): Δb* is 3.0 or more

[0202] <Warp Suppression Evaluation>

[0203] The portion of the cured product layer of the resin sheet obtained in the preparation of the evaluation sample before curing with uniform thickness was cut into 8 cm squares, and two adjacent sides of the four sides were fixed to a flat substrate with tape. The transparent resin composition layer was heated in an oven at 150°C for 90 minutes to thermally cure the transparent resin composition layer to obtain a sheet having a laminated structure of "PET film / cured product layer" (hereinafter referred to as "cured product sheet (2)"). After the cured product sheet (2) was taken out of the oven and allowed to cool, the height of the corner that was not in contact with the tape was measured (hereinafter referred to as "warping height"), and the warping suppression was evaluated according to the following criteria. The results are recorded in Table 1 below.

[0204] (Evaluation criteria for warpage suppression)

[0205] Good (○): Warping height is less than 20mm

[0206] Acceptable (△): The warping height is 20mm or more and less than 30mm

[0207] Defective (×): Warping height is 30 mm or more

[0208] <Measurement of glass transition temperature and evaluation of heat resistance>

[0209] The varnish-like transparent resin composition prepared in the examples or comparative examples was applied to the release-treated surface of a PET film ("NS80A" manufactured by Fujimori Industries) using a die coater so that the thickness of the dried transparent resin composition layer was 60 μm. The transparent resin composition layer was dried at 100° C. for 7 minutes to obtain a resin sheet having a laminated structure of "PET film / transparent resin composition layer".

[0210] After the obtained resin sheet was heated in an oven at 150°C for 30 minutes, the transparent resin composition layer was peeled off from the PET film and laminated with a PET film treated with a silicone release agent ("E7004" manufactured by Toyobo Co., Ltd.) to form a laminate. The lamination was carried out by using a vacuum laminator (V-160 manufactured by Nikko-Materials Co., Ltd.) to reduce the pressure to less than 5hPa for 20 seconds, and then pressing at 80°C and a pressure of 0.1MPa for 20 seconds. Then, the obtained laminate was further heated in an oven at 150°C for 60 minutes, and after curing the transparent resin composition layer on the PET film treated with a silicone release agent, only the cured layer was taken out. The obtained cured layer was measured in "tensile mode" using a model DMS-6100 manufactured by Seiko Instruments Co., Ltd. as a dynamic viscoelasticity measurement (DMA) device. The measurement was carried out at a temperature increase of 2°C / min in the range of 25°C to 240°C. The maximum value of the loss tangent (tan δ) determined from the ratio of the storage elastic modulus (E') and the loss elastic modulus (E") obtained in the measurement was rounded to the first decimal place, which was used as the glass transition temperature of the cured layer. Heat resistance was evaluated according to the following criteria. The results are shown in Table 1 below.

[0211] (Evaluation criteria for heat resistance)

[0212] Good (○): Glass transition temperature is 110°C or higher

[0213] Acceptable (△): Glass transition temperature is 100°C or higher and less than 110°C

[0214] Bad (×): Glass transition temperature is less than 100°C

[0215] [Table 1]

[0216]

[0217] As shown in the results described in Table 1, the transparent resin compositions of Examples 1 to 9 containing the components (A) to (C) can provide cured products having suppressed warping, excellent yellowing resistance, and excellent heat resistance.

[0218] On the other hand, a cured product having poor yellowing resistance was obtained from the transparent resin composition of Comparative Example 1 which did not contain the component (A).

[0219] In addition, from the transparent resin composition of Comparative Example 2 which does not contain the component (B), a cured product having poor warping suppression and heat resistance was obtained.

[0220] Industrial Applicability

[0221] The transparent resin composition of the present invention can be used as, for example, a sealing material, an adhesive material, etc. for transparent parts of electronic devices including LED devices and transparent FPCs.

[0222] This application is based on Japanese Patent Application No. 2023-009398 filed in Japan, the entire contents of which are incorporated herein by reference.

Claims

1. A transparent resin composition comprising the following components (A) to (C): (A) an epoxy resin having a fluoroalkyl group and / or an alicyclic structure and not having a siloxane structure, (B) an epoxy resin having a siloxane structure, and (C) Curing accelerator. The transparent resin composition according to claim 1 , further comprising a polymer compound.

3. The transparent resin composition according to claim 1 or 2, wherein The component (B) has a glycidyl group.

4. The transparent resin composition according to claim 1 or 2, wherein The content of the component (B) is 0.1 to 20% by mass relative to the nonvolatile content of the transparent resin composition.

5. The transparent resin composition according to claim 1 or 2, wherein The number of epoxy groups in one molecule of the component (B) is 2 to 10, and the epoxy equivalent of the component (B) is 150 to 350 g / mol. 6 . A resin sheet having a laminated structure comprising a support and a transparent resin composition layer formed from the transparent resin composition according to claim 1 . 7 . An electronic device comprising a cured product layer formed from the transparent resin composition according to claim 1 .

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